Device for transmitting or reproducing sound



g s. e. BROWN DEVICE FOR TRANSMITTING OR REPRODUCINCT SOUND Filed Feb. 4, 1925 2 Sheets-Sheet 1 g 23 1927. 1,639,924 Aug s. 6. BROWN 1 DEVICE FOR TRANSMITTING OR REPRODUCING SOUND 'Filed Feb. 4, 1925 2 Sheets-Sheet 2 I QX\\\\\\\\\\\\\\\\ Fig.4.

Patented Aug. 23, 1927.

SIDNEY GEORGE BROWN, OF NORTH ACTON, LONDON, ENGLAND.

DEVICE FOR TRANSMITTING OR REPBODUCING SOUND.

Application filed. February 4, 1925, Serial No. 6,870, and in Great Britain May 27, 1924.

This invention relates in general to devices for transmitting or reproducing sound. and more particularly to devices such as microphones, telephonc receivers and gramophones In devices of the kind referred to above the vibrating element is usually in the form of a disc-like diaphragm stretched over a member and clamped to this member around 10 its outer edge by suitable means, the vibrations being imparted to the centre of such diaphragm.

A certain amount of distortion of the vibrations occurs in a diaphragm of this kind owing to its having a very marked natural period of vibration and consequently the sounds produced by such a diaphragm are more or less distorted. Again, the amplitude of the vibrations of such a diaphragm is affected by the clamping around its edge.

One object is to overcome these disadvantages and the invention consists in the novel features hereinafter described and more par-- ticularly pointed out in the claims.

Referring now to the accompanying drawings which illustrate by way of example an embodiment of the invention:

igure 1 shows the top half of the vibrat- Eng element in section;

Figure 2- 'shows the bottom half of the vi brating element in section;

Figure 3 shows the vibrating element. in section;

Figure 4 shows the vibrating element applied to a loud-speaker;

Figure 5 shows the vibrating element applied to an ordinary ear telephone.

Figure 6 shows a modification of the vi brating element, and

Figure 7 shows a magnetic element at tachcd to the modified form.

In carrying the invention into eilect ac cording to one form as illustrated in ures 1 to 3, the vibrating element comprises a thin sheet metal envelope forming what 1 prefer to call a double or capsule diaphragm, the two opposing faces, a, b, of which are separated by an air space, c. Each face of my capsule diaphragm is preferably formed from a metal disc so as to have a flat annular portion, d, and a conical portion, 6, forming a depression therein, each face being a sur face of revolution.

The face, a, Figure 1, which will be hereinafter called the outer face, has the apex of the cone removed and around the hole made thereby is formed in the interior of the cone by spinning or other means a flange, f, pro ec ting upwards toward the fiat annular portion, a, in a direction parallel. to the was of said cone. The outer periphery of the flat annular portion is provided with a flange, g, parallel to the flange in the interior of the cone but pointing in the opposite direction, i. e. downwards.

The other face, I), Figure 2, hereinafter referred to as the inner face of my capsule diaphragm, is similar to the outer face, a, except that the flange, h, at the periphery of the fiat portion, (5, p ojects in the opposite direction. The two faces are pieced together with the apices of the cones on the same side and united by the flanges, g and it, which separate the two faces and form an air space between them. The top of the cone is spun over so as to form a small flat circular part. 9', parallel to the flat portion, a. The fiat or annular portion, a, of the two faces have grooves, k, spun therein to increase fiexibil-- These may be omitted if desired.

The two faces being similar, the air space. 0, between them is uniform in thickness and this thickness can he made of any desired value according to the distance separating the two faces. The capsule diaphragm is preferably enclosed in or substantially sun rounded by a casing when in use.

In applying the capsule diaphragm to a loud-speaker as illustrated in ni ure l, the fiat part, j, at the conical end of the inner face, 6, is attached to a reed. Z. or other member by ascrew or other means, the reed, i, being, given sinusoidal vibrations eiectn magnetically in the usual manner within the body or casing of the loud-speaker.

The base plate, m. to which the sound diresting means or horn oi? the loudspeaker is attached is provided with an inwardly projecting portion, 22., which has an aper ture, o, such a size that the flange, f, in the outer face, a, of the capsule diaphragm fits tightly therein. The sides of the extention, a, are made conical so as to tit accurately to the portion, a, of the outer face, a, of the capsule diaphragm and thus support the Whole of the flange. f. he rap sule diaphragm is thus suaar ally sun rounded by the body or casing of the loud speaker. Any suitable means ma be employed to rigidly secure this; lien,

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' ing or other suitable means.

horn base and means other than the abovementioned flange may be employed for securing the capsule diaphragm rigidly 1n the desired position.

Figure 5 shows the capsule diaphragm attached to an ordinary ear-piece telephone. The interior of the flange, f, and part of the outer face, a, are attached to a collar, u, while the exterior of the flange, f, is attached to a supporting member, 11, which in turn is positioned by a cylindrical member, '20, mounted upon the body, an, of the telephone. The sound directing means or earpiece, is screwed on to the body, an, and presses the member, 0, tightly against the cylindrical member w, thus forming a casing enclosing the capsule diaphragm. The faces, a and b, are united by the flanges, g and i1, and the face, 6, is attached to the reed Z, by suitable means such as a screw.

This method of attaching the capsule diaphragm may also be applied to loud-speakers.

According to a modification as illustrated in Figure 6, the two faces of the capsule diaphragm are formed of two fiat discs, p, 9, Joined together at their peripheries by a flange, r. The outer disc, p, is provided with an aperture having a flange, 8, surrounding it. This flange, s, is attached to the usual ear-piece (not shown) by expand- The face, 9, may be of magnetic material and situated directly over the magnets of the telephone, or it may be made of metal or other material and attached directly to a reed as shown in Figure 4; or a suitable magnetic member, z, ma be attached top as shown in Figure 7 which will be attracted by the telephone magnets.

The capsule diaphragm being rigidly held only at the centre of the outer face is therefore free to vibrate as a whole except at this point.

My capsule diaphragm is preferably made of thin sheet aluminium spun to the desired shape, although any other suitable metal may be employed, the two faces being spun separately and then united together by spinning, welding, soldering or any other suitable means. If desired, the capsule diaphragm can be formed by stamping, pressing or other suitable means, in one or more pieces, and need not be made of metal but of any other suitable material.

The surfaces of my capsule diaphragm may be flat, curved or any other desired shape and the two faces may be dissimilar so that the thickness of the air space can be varied at different points and the shape need not be circular but may be oval, square, polygonal or other suitable shape.

he inner face of my capsule diaphragm may be formed of a magnetic material or may have a magnetic portion attached there nesaeza to, and may be situated above the electromagnets to which the electrical impulses are supplied to cause the vibrations.

It will be seen from the description given above that the capsule diaphragm is rigidly supported only around the centre of one face and that both laces are tree to vibrato in a bellows-like manner, there being no re striction whatever at the outside edges. Such a diaphragm has no marked period oi? natural vibration and consequently it re spends accurately to any vibration which may be impressed thereon with the result that the sound vibrations emitted by such a diaphragm are substantially free from any distortion.

My capsule diaphragm as described above may be applied to any device in which a vibrating element is employed.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. A device for transmitting or reproducing sound comprising in combination a bellows-like sound capsule formed of two diaphragms joined together at their peripheries and spaced apart, one of said diaphragrns being apertured to emit sound; means for supporting one of said diaphragms in the region of its centre; a rccd attached to the other of said diaphragms in the region of its centre and on the side of the said diaphragm remote from said first-mentioned dia hragm and means for vibrating said reed.

2. A device for transmitting or reproducsound comprising in combination a bellike sound capsule formed of two dia phragms joined together at their peripheries and spaced apart, one of said diaphragins having an open sound-emitting hole at the centre thereof; a support for said diaphragms; means for rigidly sccuring said holed diaphragm to said support in the reion of said hole; a reed attached to other said diaphragms; means for vibrating said d; and a surrounding casing positioning said diaphragm support.

3. A device for transmitting or reproducing sound comprising in combination a bellows-like sound capsule formed of two diaphragms joined together at their peripheries and spaced apart, one of said diaphragms having an open sound-omitting hole at the centre thcreot; means for supporting said diaphragm in the region of said hole; a reed attached to the other of said diaphragms and disposed on the side thereof. remote from said firstanentioned diaphragm and means for vibrating said reed.

l. In a device for transmitting or reproducin sound, the combination comprising a vibrating element composed of two opposed diaphragnis connected, together at their peripheries to form an enclosed space, each dialOU - phragm having a conical portion and a flat annular portion, a casing substantially surrounding said element, means for rigidly attaching the conical portion of one of said diaphragms to said casing, and means for imparting vibrations to the other of said diaphragms, as set forth. 5. In a dance for transmitting-or. reproducln sound, the combination comprising a vibrating element having two similar diaphragms opposed to one another, means for connecting said diaphragms to ether at their peripheries to form an enclose space of uniorm thickness, means'for directly causing one of said diaphragms to vibrate, a directing member; and means for 'rigidly connecting the centre of said other diaphragm to said sound directing member, as set forth.

6. In a device for transmitting or reproducing sound, the combination comprising a vibrating element composed of two opposed diaphragms connected together at their peripheries-to form a bellows-like sound capsule, each diaphragm having a conical portion and a fiat annular portion, one of said diaphragms being apertured to emit sound, a casing substantiall surrounding said element, means for rigi 1y attaching the conical portion of one of said diaphragms to said casing a. reed attached to the conical portion of the other of said diaphrag'ms and means for imparting vibrations to said reed, as set forth.

In testimony whereof I have signed my name to this specification.

SIDNEY GEORGE BROWN. 

